A polyether polymer can be defined as a polymer containing ether bonds in its repeating units. There are known many polyether polymers having various characteristics, such as a polyether ether ketone known as an industrial material, and polyethylene glycol (see KOBUNSHI DAIJITEN, page 1038, published by MARUZEN Co., LTD. Sep. 20, 1994; “KOBUNSHI DAIJITEN” means “POLYMER COMPREHENSIVE DICTIONARY”).
There are known polyphenylene ethers as a polyether polymer containing ether bonds and aromatic ring structures. Poly(2,6-dimethyl-1,4-phenylene ether), which is an example of the polyphenylene ethers, has a good thermal property such as good ductibility even at a lower temperature than its Tg, and high impact resistance even at −200° C. or lower, and is a good physical property-carrying material having good ductibility, high strength, and high heat distortion temperature (see KOBUNSHI DAIJITEN, page 1067, published by MARUZEN Co., LTD. Sep. 20, 1994).